1. Field of the Invention
This invention relates to the field of Mycotoxin assays. More particularly, this invention relates to a homogeneous assay that uses changes in fluorescence polarization to detect the presence of fumonisin in grains.
2. Description of Related Art
Fumonisins are mycotoxins produced mainly by Fusarium moniliforme, a common fungus found mostly in corns and corn products. Several different fumonisins have been identified, including fumonisin B1, B2, B3, and B4, and these are all characterized by a 20-carbon backbone, two tricarballylic acid groups, one to three hydroxyl groups, and a single primary amine. Fumonisin B1 is believed to be the most abundant form.
Fumonisin is the cause of leukoencephalomalacia (which is also referred to as LEM or spongy brain syndrome) in horses, cancer in laboratory animals, and esophageal cancer in humans.1 Fumonisin levels greater than 10 parts per million (PPM) cause craziness in horses within a week, and levels greater than about 70 PPM can cause various liver diseases in pigs within four weeks. Due to the possible risk to human and animal health, extended research is underway to develop effective procedures for the determination of fumonisins.8 
Being new, this toxin lacks a simple commercially available test kit for its quantitative analysis. Mass spectroscopy,1b TLC,9 HPLC,2-4 and ELISA (enzyme-linked immunosorbent assay)7 are the known methods for fumonisin analysis. However, most of these assays require extended cleanup steps and derivatization after extraction in order to get rid of interfering substances. This becomes very time consuming and in turn hampers the fast analysis of fumonisins.
ELISA methods are relatively faster. However, they are hard to quantify and have limitations due to dilution and washing steps. ELISA methods are also undesirably labor intensive, in that they typically involve several washings, liquid transfers, and incubation times. Nevertheless, specific antibodies against fumonisin have been prepared by various groups.10-11 Due to various limitations of different methods; a faster and simpler method for the determination of fumonisins is needed.
In a first principal aspect, the present invention provides a homogeneous assay for characterizing the fumonisin content in grains. In accordance with the method, fumonisin is extracted from a grain sample to provide an extract. The extract is then combined with a tracer and an antibody to provide a mixture. The antibody is specific for fumonisin. The tracer comprises fumonisin conjugated to a fluorophore, and the tracer is able to bind to the antibody to produce a detectable change in fluorescence polarization. The fluorescence polarization of the mixture is measured to obtain a measured fluorescence polarization. The measured fluorescence polarization is compared with a characterized fluorescence polarization value that corresponds to a known fumonisin concentration.
In a second principal aspect, the present invention provides an assay kit for characterizing fumonisin content in grains. The assay kit comprises an antibody and a tracer, each in an amount suitable for at least one assay, and suitable packaging. The antibody is specific for fumonisin. The tracer comprises fumonisin conjugated to a fluorophore, and the tracer is able to bind to the antibody to produce a detectable change in fluorescence polarization.